U.S. patent number 5,758,487 [Application Number 08/746,165] was granted by the patent office on 1998-06-02 for gas turbine engine with air and steam cooled turbine.
This patent grant is currently assigned to Rolls-Royce plc. Invention is credited to Alan Cash, Allan J. Salt, Carlton Smith.
United States Patent |
5,758,487 |
Salt , et al. |
June 2, 1998 |
Gas turbine engine with air and steam cooled turbine
Abstract
In a gas turbine engine including a turbine which has a closed
cycle steam cooling system and an open cycle gas cooling system
sealing arrangements are provided between adjacent pairs of turbine
rotor stages. The sealing arrangement has axially extending
passages to supply cooling gas from one of the turbine rotor stages
to the cooling gas passages in the turbine rotor blades. Each
sealing arrangement comprises a pair of sealing formations each
made up of a plurality of sealing segments. Also the sealing
arrangement has axially extending passages to supply steam from one
of the turbine rotor stages to the steam cooling passages in the
turbine rotor blades.
Inventors: |
Salt; Allan J. (Warwickshire,
GB2), Cash; Alan (Leicestershire, GB2),
Smith; Carlton (Huddersfield, GB2) |
Assignee: |
Rolls-Royce plc (London,
GB2)
|
Family
ID: |
10783820 |
Appl.
No.: |
08/746,165 |
Filed: |
November 6, 1996 |
Foreign Application Priority Data
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Nov 14, 1995 [GB] |
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9523223 |
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Current U.S.
Class: |
60/806;
415/114 |
Current CPC
Class: |
F01D
5/084 (20130101); F02C 7/16 (20130101); F02C
7/18 (20130101); F05D 2260/2322 (20130101) |
Current International
Class: |
F01D
5/02 (20060101); F01D 5/08 (20060101); F02C
7/16 (20060101); F02C 7/18 (20060101); F02C
007/16 () |
Field of
Search: |
;60/39.07,39.182,39.53,39.54,39.75 ;415/115 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 127 906 |
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Apr 1984 |
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GB |
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2 137 283 |
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Oct 1984 |
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GB |
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2 224 319 |
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May 1990 |
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GB |
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2 253 442 |
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Sep 1992 |
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GB |
|
Primary Examiner: Casaregola; Louis J.
Attorney, Agent or Firm: Cushman Darby & Cushman
Intellectual Property Group of Pillsbury Madison & Sutro
LLP
Claims
We claim:
1. A gas turbine engine including a multi-stage turbine having a
first cooling system and a second cooling system, said engine
comprising a first rotor stage having a plurality of first turbine
rotor blades, each first turbine rotor blade having a first passage
for the flow of a first cooling fluid and a second passage for the
flow of a second cooling fluid, a second rotor stage having a
plurality of second turbine rotor blades, each second turbine rotor
blade having a third passage for the flow of the first cooling
fluid and a fourth passage for the flow of the second cooling
fluid, a first sealing arrangement extending axially between the
first and second rotor stages, a first chamber formed between the
first and second rotor stages and the first sealing arrangement,
the first sealing arrangement having at least one passage extending
axially between the first and second rotor stages to supply the
first cooling fluid between the first and second rotor stages, the
first cooling system being arranged to supply first cooling fluid
to the first passages in the first turbine rotor blades and being
arranged to supply first cooling fluid through the at least one
passage extending axially through the first sealing arrangement to
the third passages in the second turbine rotor blades.
2. A gas turbine engine as claimed in claim 1 wherein the
multi-stage turbine has a closed cycle steam cooling system and an
open cycle gas cooling system, each first turbine rotor blade
having a first passage for the flow of gas and a second closed
passage for the flow of steam, each first turbine blade has a
trailing edge which is open to discharge gas from the first passage
through the trailing edge of the first turbine rotor blade, each
second turbine rotor blade having a third passage for the flow of
gas and a fourth closed passage for the flow of steam, each second
turbine blade having a trailing edge which is open to discharge gas
from the third passage through the trailing edge of the second
turbine rotor blade, a first sealing arrangement extending axially
between the first and second rotor stages.
3. A gas turbine engine as claimed in claim 2 wherein the
multi-stage turbine has a closed cycle steam cooling system and an
open cycle gas cooling system, each first turbine rotor blade
having a first closed passage for the flow of steam and a second
passage for the flow of gas, each first turbine blade has a
trailing edge which is open to discharge gas from the second
passage through the trailing edge of the first turbine rotor blade,
each second turbine rotor blade having a third closed passage for
the flow of steam and a fourth passage for the flow of gas, each
second turbine blade has a trailing edge which is open to discharge
gas from the fourth passage through the trailing edge of the second
turbine rotor blade, a first sealing arrangement extending axially
between the first and second rotor stages.
4. A gas turbine engine as claimed in claim 3 comprising means to
supply cooling gas to the first passages in the first turbine rotor
blades and the at least one passage in the first sealing
arrangement, said at least one passage in the first sealing
arrangement being arranged to supply cooling gas to the third
passages in the second turbine rotor blades, means to supply steam
to the first passages in the first turbine rotor blades and the
first passages being arranged to supply steam to the second
chamber.
5. A gas turbine engine as claimed in claim 3 comprising means to
supply steam to the first passages in the first turbine rotor
blades and the at least one passage in the first sealing
arrangement, said at least one passage in the first sealing
arrangement being arranged to supply steam to the third passages in
the second turbine rotor blades, means to supply cooling gas to the
second passages in the first turbine rotor blades and means to
supply cooling gas to the fourth passages in the second turbine
rotor blades.
6. A gas turbine engine as claimed in claim 4 comprising a third
rotor stage having a plurality of third turbine rotor blades, each
third turbine rotor blade having a fifth passage for the flow of
air and a sixth closed passage for the flow of steam, each third
turbine rotor blade has a trailing edge which is open to discharge
gas from the fifth passage through the trailing edge of the third
turbine rotor blade, a second sealing arrangement extending axially
between the second and third rotor stages, the second sealing
arrangement having at least one passage extending axially between
the second and third rotor stages, the second sealing arrangement
having at least one passage extending axially between the second
and third rotor stages, a second chamber formed between the second
and third rotor stages and the second sealing arrangement, the at
least one passage in the first sealing arrangement being arranged
to supply cooling gas to the second chamber, the second chamber
supplying cooling gas to the fifth passages in the third turbine
rotor blades, means to supply steam to the sixth passages in the
third turbine rotor blades, the sixth passages being arranged to
supply steam to the at least one passage in the second sealing
arrangement, said at least one passage in the second sealing
arrangement being arranged to supply steam to the fourth passages
in the second turbine rotor blades and the fourth passages being
arranged to supply steam to the first chamber.
7. A gas turbine engine as claimed in claim 6 wherein the third
rotor stage is axially downstream of the second turbine rotor stage
and the second turbine rotor stage is axially downstream of the
first turbine rotor stages.
8. A gas turbine engine as claimed in claim 2 wherein the sealing
arrangements between two axially spaced adjacent turbine rotor
stages includes, on each turbine rotor stage, a circumferentially
extending sealing formation extending from the turbine rotor stage
axially towards the other turbine rotor stage and bridging part of
the axial space between the two turbine rotor stages, the two
sealing formations having free ends which cooperate to form a seal
and each sealing formation comprising a plurality of segments, the
turbine rotor stages having serrations in their periphery, the
segments locating in the turbine rotor stage serrations.
9. A gas turbine engine as claimed in claim 8 wherein the turbine
rotor blades locate in the turbine rotor stage serrations, and the
turbine rotor blades have blade platforms, the sealing arrangements
are each about half the blade platform to blade platform spacing in
axial extent.
10. A gas turbine engine as claimed in claim 8 wherein each sealing
segment comprises a body having a radially inner root portion
provided with serrations complementary to the serrations provided
in the periphery of the turbine rotor stage, and a column extending
radially from such root portion, a relatively thin sealing panel
which provides outwardly extending fins for sealing engagement with
platforms on the inner ends of cooperating stator vanes, the column
supports the thin sealing panel.
11. A gas turbine engine as claimed in claim 10 wherein the panel
has a generally axially extending spine united with its column.
12. A gas turbine engine as claimed in claim 1 wherein each sealing
segment is mounted by a root which engages the same turbine rotor
stage serration, or serrations, as a root of a turbine rotor blade
and each sealing segment is connected to its respective turbine
rotor blade to restrain it against axial movement out of the
serration, or serrations.
13. A gas turbine engine as claimed in claim 12 wherein the
connection is by means of a dovetail slot, or a T-slot.
14. A gas turbine engine as claimed in claim 11 wherein the spines
of the sealing segments are hollow to define axially extending
passages for the flow of cooling fluid, the axially extending
passages in the spines on the sealing segments on the upstream
rotor disc are in alignment with the axially extending passages in
the spines on the sealing segments on the downstream rotor
disc.
15. A gas turbine engine as claimed in claim 14 wherein the bodies
of the sealing segments on at least one of the upstream rotor disc
or the downstream rotor disc are hollow to define radially
extending passages for the flow of cooling fluid.
16. A gas turbine engine as claimed claim 1 herein at least one
sealing plate is located between at least one of the sealing
arrangements and the corresponding turbine rotor stage.
17. A gas turbine engine as claimed in claim 16 wherein there are a
plurality of sealing plates, each sealing plate locates in a recess
in a respective one of the sealing arrangements.
18. A gas turbine engine including a multi-stage turbine having a
closed cycle steam cooling system and an open cycle gas cooling
system, said engine comprising a first rotor stage having a
plurality of first turbine rotor blades, each first turbine rotor
blade having a first closed passage for the flow of steam and a
second passage for the flow of gas, each first turbine blade having
a trailing edge which is open to discharge the gas from the second
passage through the trailing edge of the first turbine rotor blade,
a second rotor stage having a plurality of second turbine rotor
blades, each second turbine rotor blade having a third closed
passage for the flow of steam and a fourth passage for the flow of
gas, each second turbine blade having a trailing edge which is open
to discharge the gas from the fourth passage through the trailing
edge of the second turbine rotor blade, a first sealing arrangement
extending axially between the first and second rotor stages, the
first sealing arrangement having at least one passage extending
axially between the first and second rotor stages, a first chamber
formed between the first and second rotor stages and the first
sealing arrangement, means to supply cooling gas to the second
passages in the first turbine rotor blades and the at least one
passage in the first sealing arrangement, said at least one passage
in the first sealing arrangement being arranged to supply cooling
gas to the fourth passages in the second turbine rotor blades,
means to supply steam to the first passages in the first turbine
rotor blades and the first passages being arranged to supply steam
to the first chamber.
19. A gas turbine engine as claimed in claim 18 comprising a third
rotor stage having a plurality of third turbine rotor blades, each
third turbine rotor blade having a fifth closed passage for the
flow of steam and a sixth passage for the flow of gas, each third
turbine blade having a trailing edge which is open to discharge the
gas from the sixth passage through the trailing edge of the third
turbine rotor blade, a second sealing arrangement extending axially
between the second and third rotor stages, the second sealing
arrangement having at least one passage extending axially between
the second and third rotor stages, a second chamber formed between
the second and third rotor stages and the second sealing
arrangement, the at least one passage in the first sealing
arrangement being arranged to supply cooling gas to the second
chamber, the second chamber supplying cooling gas to the sixth
passages in the third turbine rotor blades, means to supply steam
to the fifth passages in the third turbine rotor blades, the fifth
passages being arranged to supply steam to the at least one passage
in the second sealing arrangement, said at least one passage in the
second sealing arrangement being arranged to supply steam to the
third passages in the second turbine rotor blades and the third
passages being arranged to supply steam to the first chamber.
Description
FIELD OF THE INVENTION
The present invention relates to a gas turbine engine, particularly
to a gas turbine engine in which the turbine blades are provided
with cooling passages supplied with cooling fluids at different
pressures or different cooling fluids. The present invention in
particular relates to industrial gas turbine engines having a
closed cycle steam cooling system and an open cycle gas cooling
system.
BACKGROUND OF THE INVENTION
Industrial gas turbine engines generally comprise a gas generator
consisting of a compressor, a combustion apparatus in which fuel
and air are mixed and burnt, a turbine which is driven by the
products of combustion and which drives the compressor, and a power
turbine driven by the high temperature high velocity gases from the
gas generator. The power turbine is arranged to drive loads such as
an electricity generator, or pump for pumping oil or gas.
Heavyweight industrial gas generators are bulky and there are large
distances between the bearings of a shaft on which the compressor
and turbine are mounted. The turbine and a gas generator will
comprise one or more stages of blades, each stage comprising an
array of rotor blades mounted on the gas generator shaft and an
array of stator vanes mounted from the casing of the gas generator.
The high temperature, high velocity gases flow through an annular
passage in which the rotating rotor blades and stationary stator
vanes are disposed and the radially inner boundary of the annular
passage is partially defined by platforms on the inner ends of the
stator vanes. These platforms are usually sealingly engaged by
sealing elements secured to rotors on which the rotor blades are
located.
In the case of relatively low power engines a seal can be achieved
by casting projections or "wings", otherwise known as heat shields,
onto the platforms at the inner ends of the rotor blades. These
projections on the rotor blades on adjacent stages abut one another
to form a seal. In the case of relatively large power engines a
seal can be achieved by providing separate sealing segments which
extend between adjacent rotors. The sealing segments are provided
with axially extending dogs which engage underneath axial
projections on the rotors, as is disclosed in our published UK
patent application No 2272946A. Also in the case of relatively
large power engines a seal can be achieved by providing separate
sealing segments which extend between adjacent rotors. The sealing
segments are provided with axially extending feet which engage
between inner and outer lands on the rotors, as is disclosed in our
published UK patent application No 2272947A. A further possibility
in the case of relatively large power engines a seal can be
achieved by providing separate sealing segments which extend
between adjacent rotors. The sealing segments are provided with
serrated feet which engage in the blade root slots, as is disclosed
in our published UK patent application No 2280478A.
In a gas turbine engine including a turbine having a closed cycle
steam cooling system and an open cycle air cooling system it is
difficult to arrange for the steam and air cooling system to supply
the blades on the different turbine rotor stages without leakage of
steam into the air or visa-versa. This requirement also applies to
the use of the same cooling fluid at different pressures.
SUMMARY OF THE INVENTION
The present invention seeks to provide a gas turbine engine which
overcomes the above mentioned problem.
Accordingly the present invention provides a gas turbine engine
including a multi-stage turbine having a first cooling system and a
second cooling system, said engine comprising a first rotor stage
having a plurality of first turbine rotor blades, each first
turbine rotor blade having a first passage for the flow of a first
cooling fluid and a second passage for the flow of a second cooling
fluid, a second rotor stage having a plurality of second turbine
rotor blades, each second turbine rotor blade having a third
passage for the flow of the first cooling fluid and a fourth
passage for the flow of the second cooling fluid, a first sealing
arrangement extending axially between the first and second rotor
stages, a first chamber formed between the first and second rotor
stages and the first sealing arrangement, the first sealing
arrangement having at least one passage extending axially between
the first and second rotor stages to supply the first cooling
fluid, or the second cooling fluid, between the first and second
rotor stages such that the second passages or fourth passages are
supplied with the second cooling fluid or the first passages or the
third passages are supplied with the first cooling fluid.
Preferably the first cooling fluid is steam and the second cooling
fluid is gas.
Preferably the multi-stage turbine has a closed cycle steam cooling
system and an open cycle gas cooling system, each first turbine
rotor blade having a first closed passage for the flow of steam and
a second passage for the flow of gas which is open to discharge the
gas from the trailing edge of the first turbine rotor blade, each
second turbine rotor blade having a third closed passage for the
flow of steam and a fourth passage for the flow of gas which is
open to discharge the gas from the trailing edge of the second
turbine rotor blade, a first sealing arrangement extending axially
between the first and second rotor stages.
Preferably there are means to supply cooling gas to the second
passages in the first turbine rotor blades and the at least one
passage in the first sealing arrangement, said at least one passage
in the first sealing arrangement being arranged to supply cooling
gas to the fourth passages in the second turbine rotor blades,
means to supply steam to the first passages in the first turbine
rotor blades and the first passages being arranged to supply steam
to the first chamber.
Alternatively there may be means to supply steam to the first
passages in the first turbine rotor blades and the at least one
passage in the first sealing arrangement, said at least one passage
in the first sealing arrangement being arranged to supply steam to
the third passages in the second turbine rotor blades, means to
supply cooling gas to the second passages in the first turbine
rotor blades and means to supply cooling gas to the fourth passages
in the second turbine rotor blades.
Preferably there is a third rotor stage having a plurality of third
turbine rotor blades, each third turbine rotor blade having a fifth
closed passage for the flow of steam and a sixth passage for the
flow of gas which is open to discharge the gas from the trailing
edge of the third turbine rotor blade, a second sealing arrangement
extending axially between the second and third rotor stages, the
second sealing arrangement having at least one passage extending
axially between the second and third rotor stages, a second chamber
formed between the second and third rotor stages and the second
sealing arrangement, the at least one passage in the first sealing
arrangement being arranged to supply cooling gas to the second
chamber, the second chamber supplying cooling gas to the sixth
passages in the third turbine rotor blades, means to supply steam
to the fifth passages in the third turbine rotor blades, the fifth
passages being arranged to supply steam to the at least one passage
in the second sealing arrangement, said at least one passage in the
second sealing arrangement being arranged to supply steam to the
third passages in the second turbine rotor blades and the third
passages being arranged to supply steam to the first chamber.
Preferably the third rotor stage is axially downstream of the
second turbine rotor stage and the second turbine rotor stage is
axially downstream of the first turbine rotor stage.
Preferably the sealing arrangements between two adjacent turbine
rotor stages includes, on each turbine rotor stage, a
circumferentially extending sealing formation extending from the
turbine rotor stage axially towards the other disc and bridging
part of the space between the two turbine rotor stages, free ends
of the two sealing arrangements cooperating to form a seal and each
sealing arrangement comprising a plurality of segments, the
segments locating in the rotor disc serrations.
Preferably the sealing arrangements are each about half the blade
platform to blade platform spacing in axial extent.
Preferably each sealing segment comprises a body having a radially
inner root portion provided with serrations complementary to the
serrations provided in the periphery of the turbine rotor disc, and
a column extending radially from such root portion supports a
relatively thin sealing panel which provides outwardly extending
fins for sealing engagement with platforms on the inner ends of the
stator vanes.
Preferably the panel has a generally axially extending spine united
with its column.
Preferably each sealing segment is mounted by a root which engages
the same disc serration, or serrations, as a root of a turbine
rotor blade and each sealing segment is connected to its respective
turbine rotor blade to restrain it against axial movement out of
the serration, or serrations.
Preferably the connection is by means of a dovetail slot, or a
T-slot.
Preferably the spines of the sealing segments are hollow to define
axially extending passages for the flow of cooling fluid, the
axially extending passages in the spines on the sealing segments on
the upstream rotor disc are in alignment with the axially extending
passages in the spines on the sealing segments on the downstream
rotor disc .
Preferably the bodies of the sealing segments on at least one of
the upstream rotor disc or the downstream rotor disc are hollow to
define radially extending passages for the flow of cooling
fluid.
Preferably at least one sealing plate is located between at least
one of the sealing arrangements and the corresponding turbine rotor
stage.
Preferably there are a plurality of sealing plates, each sealing
plate locates in a recess a respective one of the sealing
arrangements.
The present invention also provides a gas turbine engine including
a multi-stage turbine having a closed cycle steam cooling system
and an open cycle gas cooling system, said engine comprising a
first rotor stage having a plurality of first turbine rotor blades,
each first turbine rotor blade having a first closed passage for
the flow of steam and a second passage for the flow of gas which is
open to discharge the gas from the trailing edge of the first
turbine rotor blade, a second rotor stage having a plurality of
second turbine rotor blades, each second turbine rotor blade having
a third closed passage for the flow of steam and a fourth passage
for the flow of gas which is open to discharge the gas from the
trailing edge of the second turbine rotor blade, a first sealing
arrangement extending axially between the first and second rotor
stages, the first sealing arrangement having at least one passage
extending axially between the first and second rotor stages, a
first chamber formed between the first and second rotor stages and
the first sealing arrangement, means to supply cooling gas to the
second passages in the first turbine rotor blades and the at least
one passage in the first sealing arrangement, said at least one
passage in the first sealing arrangement being arranged to supply
cooling gas to the fourth passages in the second turbine rotor
blades, means to supply steam to the first passages in the first
turbine rotor blades and the first passages being arranged to
supply steam to the first chamber.
Preferably there is a third rotor stage having a plurality of third
turbine rotor blades, each third turbine rotor blade having a fifth
closed passage for the flow of steam and a sixth passage for the
flow of gas which is open to discharge the gas from the trailing
edge of the third turbine rotor blade, a second sealing arrangement
extending axially between the second and third rotor stages, the
second sealing arrangement having at least one passage extending
axially between the second and third rotor stages, a second chamber
formed between the second and third rotor stages and the second
sealing arrangement, the at least one passage in the first sealing
arrangement being arranged to supply cooling gas to the second
chamber, the second chamber supplying cooling gas to the sixth
passages in the third turbine rotor blades, means to supply steam
to the fifth passages in the third turbine rotor blades, the fifth
passages being arranged to supply steam to the at least one passage
in the second sealing arrangement, said at least one passage in the
second sealing arrangement being arranged to supply steam to the
third passages in the second turbine rotor blades and the third
passages being arranged to supply steam to the first chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described further, by way of example, with
reference to the accompanying drawings, wherein:
FIG. 1 shows diagrammatically an industrial gas turbine engine.
FIG. 2 shows part of a gas turbine incorporating a multi-stage
turbine having a combined closed cycle steam cooling system and
open cycle gas cooling system according to the present
invention.
FIG. 3 is a perspective view of a sealing segment shown in FIG.
2.
FIG. 4 is a perspective view of a turbine rotor blade shown in FIG.
2, and
FIG. 5 is a perspective view of a sealing plate shown in FIG.
2.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, in FIG. 1 there is shown an industrial
gas turbine power plant 10 comprising a gas generator 12 and a
power turbine 14 arranged to drive a load 16 which may be for
example an electricity generator or a pump. The gas generator 12
comprises, in axial flow series, a compressor 18, a combustor 20
and a turbine 22 mounted on a common shaft with the compressor 18.
High temperature, high velocity gas produced in the gas generator
12 by combustion of fuel and compressed air in the combustor 20,
drives turbine 22, which drives the compressor 18 through the
common shaft. The excess power in the turbine gases after passage
through the turbine 22 is used to drive the power turbine 14.
In FIG. 2 is shown a combined closed cycle steam cooling system and
an open cycle gas cooling system in the turbine of an industrial
gas turbine engine. which the sealing segments are provided with
axially extending spines at the circumferentially central region of
the panels. Steam is supplied in a closed cycle loop to cooling
passages at least at the leading edge, or central region, of the
turbine rotor blades and air is supplied in an open cycle to
cooling passages at least at the trailing edge of the turbine rotor
blades. The cooling air is discharged from the cooling passages at
the trailing edge of the turbine rotor blades into the working
fluid.
The first stage rotor disc 200 carries turbine rotor blades 206,
the second stage rotor disc 202 carries turbine rotor blades 208
and the third stage rotor disc 204 carries turbine rotor blades
210. A first set of sealing segments 212 extends in a downstream
direction from the first rotor disc 200 and a second set of sealing
segments 214 extends in an upstream direction from the second rotor
disc 202. Similarly a third set of sealing segments 216 extends in
a downstream direction form the second rotor disc 202 and a fourth
set of sealing segments 218 extends in an upstream direction from
the third rotor disc 204. A chamber 220 is formed between the first
and second rotor discs 200 and 202, and a chamber 222 is formed
between the second and third rotor discs 202 and 204.
Steam is supplied through passages 224 and along serrations in the
first rotor disc 200 to the passages 226 at the leading edge of the
turbine rotor blades 206. The steam is returned from the passages
226 in the turbine rotor blades 206 through passages 228 in the
first rotor disc 200 to the chamber 220. A plurality of seal plates
230 are provided between the sealing segments 212 and the turbine
rotor blades 206 to separate the chamber 220 from the spaces 232
between the shanks of the turbine rotor blades 206.
Air is supplied to the spaces 232 between the shanks of the turbine
rotor blades 206 and a first portion of the air flows into cooling
air passages 209 at the trailing edges of the turbine rotor blades
206. A second portion of the air supplied to the spaces 232 flows
through apertures 234 in the seal plates 230 to the axially
extending passages 236 in the spines 238 of the sealing segments
212. The air supplied to the passages 236 flows into axially
extending passages 240 in the spines 242 of the sealing segments
214. A plurality of seal plates are provided between the sealing
segments 214 and the turbine rotor blades 208 to separate the
chamber 220 from the spaces 244 between the shanks of the turbine
rotor blades 208. The cooling air flowing through the passages 240
flows into the spaces 244 between the shanks of the turbine rotor
blades 208 and a first portion of the cooling air flows into
cooling air passages 211 at the trailing edges of the turbine rotor
blades 208. The remaining portion of the air supplied to the spaces
244 flows into the chamber 222. The cooling air flowing through the
cooling air passages at the trailing edge of the turbine blades is
discharged into the gas flow.
Steam is supplied along the serrations in the third rotor disc 204
to the passages 246 at the leading edge of the turbine rotor blades
210. The steam is returned from the passages 246 in the turbine
rotor blades 210 and along the serrations in the third rotor disc
204 to the sealing segments 218. The sealing segments 218 have
radially extending passages 248 in their bodies 250 and axially
extending passages 252 in their spines 254. The passages 252 align
with axially extending passages 256 in the spines 258 of the
sealing segments 216. The sealing segments 216 also have radially
extending passages 260 in their bodies 262. The passages 248, 252,
256 and 260 convey cooling steam to the serrations in the second
rotor disc 202. The steam then flows to the passages 264 at the
leading edge of the turbine rotor blades 208. The steam is returned
from the passages 264 to the serrations and is discharged through
passages 266 in the second rotor disc 202 to the chamber 220.
Air is supplied from chamber 222 into the spaces 268 between the
shanks of the turbine rotor blades 210 and a portion of the air
flows into cooling air passages 213 at the trailing edges of the
turbine rotor blades 210. The cooling air flowing through the
cooling air passages at the trailing edge of the turbine blades is
discharged into the gas flow. The remainder of the cooling air in
the spaces 268 between the shanks of the turbine rotor blades 210
is discharged in a downstream direction for further cooling
purposes.
In FIG. 2 the first stage rotor disc 200 has serrations 270, each
of which receives the root 272 of one of the plurality of turbine
rotor blades 206. Similarly the second stage rotor disc 202 has
serrations 274, each of which receives the root 276 of one of the
plurality of turbine rotor blades 208. Also the third stage rotor
disc 204 has serrations 278, each of which receives the root 280 of
one of the turbine rotor blades 210.
Each of the serrations 270 also receives a root 282 of one of the
plurality of circumferentially arranged sealing segments 212.
Similarly each of the serrations 274 receives a root 284 of one of
the plurality of circumferentially arranged sealing segments 214
and also receives a root 286 of one of the plurality of
circumferentially arranged sealing segments 216. Additionally each
of the serrations 278 receives a root 288 of one of the plurality
of circumferentially arranged sealing segments 218. Each sealing
segment has a main operative panel 285 carrying sealing ribs which
cooperate, in conventional manner, with surfaces on the platforms
of stator vanes.
The panels are relatively thin to render the segments of relatively
low weight and therefore centrifugal forces are reduced. The panels
are usually a segment of a cone or a segment of a cylinder.
All of the sealing segments 212, 214 unite to form a frusto-conical
sealing formation or a cylindrical sealing formation which extends
axially between the first stage rotor disc 200 and the second stage
rotor disc 202. All of the sealing segments 216, 218 unite to form
a frusto-conical sealing formation or a cylindrical sealing
formation which extends axially between the second stage rotor disc
202 and the third stage rotor disc 204. The free edges of the two
formations are sealingly engaged and provide an effective heat
shield and sealing arrangement on the internal periphery of the
annular gas flow passage.
The ribs on the circumferentially adjacent sealing segments unite
to form circumferentially extending sealing fins.
In order to guard against the centrifugal force withdrawing the
roots 282, 284, 286 and 288 of the sealing segments 212, 214, 216,
218 respectively from the serrations 270, 274 and 278 respectively,
the roots 282, 284, 286 and 288 of the sealing segments 212, 214,
216 and 218 respectively and the adjacent roots 272, 276, 280 of
the respective turbine rotor blades 206, 208 and 210 are provided
with complementary positive interlocking formations which lock the
roots of the sealing segments to the roots of the turbine rotor
blades and prevent the roots of the sealing segments from leaving
the serrations of the respective turbine rotor disc.
The interlocking formations may take any convenient form, but a
dovetail or a T-slot connection is desirable.
FIGS. 3 and 4 show the root 272 of the turbine rotor blade 206
provided within a dovetail tongue 290 which engages in a dovetail
slot 292 in the root 282 of the sealing segment 212. It is of
course possible to provide the tongue on the sealing segment and
the slot on the blade.
Other variations are possible, for example one of the roots may be
provided with a tennon and the other a mortice, a fastener or
fasteners being passed through the two to unite the tennon and the
mortice.
It may be possible to arrange for other arrangements of cooling
flow in the roots, spines and body and columns 281 of the sealing
segments.
FIG. 5 shows a sealing plate 230 which locates in the recess of a
sealing segment 212.
It is of course possible to provide axially extending passages in
other types of sealing segments, for example the sealing segments
described in GB2272946A, GB2279947A or GB2280478A the contents of
which are hereby incorporated by reference.
Thus it can be seen that by providing the axially extending
passages in the sealing arrangement between adjacent turbine rotor
stages it is possible to arrange for the steam and cooling gas to
be supplied to the turbine rotor blades without the leakage of
steam into the gas or visa-versa. The cooling gas is preferably air
from the compressor of the gas turbine engine.
The axially extending passages in the sealing arrangement between
adjacent turbine rotor stages may also be used to for other
different cooling fluids, or the same cooling fluid but at
different pressures, to enable the cooling fluids to be supplied to
the respective passages in the turbine rotor blades without the
cooling fluids intermingling.
* * * * *